... for (p = fis->node[i]->fanout; p != NULL; p = p->next) {
/* O_i is the k-th fanin of O_{p->index} --> find k */
for (k = 0, q = fis->node[p->index]->fanin; q->index != i; q = q->next, k++);
if (k >= fis->node[p->index]->fanin_n)
fisError("...
